二次选择指数及其在猪育种中的应用

综合育种值的二次数学模型包括各性状育种值的一次项、二次项和交互项。在二次育种值模型下,可以使用线性选择指数或二次选择指数。但二次选择指数的效率总是高于线性选择指数。二次育种值模型下的选择指数具有通用性,通常的线性选择指数是这种选择指数的特殊形式。我国本地猪瘦肉型品系选育的选择指数包括日增重和背膘厚两性状。对背膘厚的二次项进行负的经济加权,使膘厚不是无限制的下降,当膘厚低于一定值时,其育种值便有所下降,从而保证肉的品质不致因膘过薄、瘦肉率过高而变差。

Selection Indics for Quadratic Models of Total Merit and Its Application in Swine Breeding

The quadratic models of total merit include squares and crossproducts as well as first-powers of the traits involved A liner and a quadratic index are developed as selection criteria forthe quadratic models of total merit, but the selection efficiency of the liner index is alway less than that of the quadratic index. The index for the quadratic models of total merit are ot wider usage than the usual selection index for a liner additive model ot merit, the later is the special form of the former. The index of native pig specises consists of the body weight per day and backfat thickness If the square of backfat thickness was weighted negatively, selection is for an intermediate genotype. This can avoidproducting bad meal quality which results from too low backfat thickness and high lean percentage.